<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>条件语句</title>
</head>

<body>

    <script>
	    var box = 100;
	    if (box >= 100) {
	        alert("甲");
	    } else if (box >= 90) {
	        alert("乙");
	    } else if (box >= 80) {
	        alert("丙");
	    } else if (box >= 70) {
	        alert("丁");
	    } else if (box >= 60) {
	        alert("及格");
	    } else {
	        alert("不及格");
	    }
    </script>
    
</body>

</html>